US6601676B2 - Self-lubricating ballscrew - Google Patents

Self-lubricating ballscrew Download PDF

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Publication number
US6601676B2
US6601676B2 US09/745,052 US74505200A US6601676B2 US 6601676 B2 US6601676 B2 US 6601676B2 US 74505200 A US74505200 A US 74505200A US 6601676 B2 US6601676 B2 US 6601676B2
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United States
Prior art keywords
lubricating
self
screwshaft
ballscrew
section
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related, expires
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US09/745,052
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US20010018850A1 (en
Inventor
Dennis Frederick Walton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thomson Saginaw Ball Screw Co LLC
Original Assignee
Thomson Saginaw Ball Screw Co LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Assigned to THOMSON SAGINAW BALL SCREW COMPANY, LLC reassignment THOMSON SAGINAW BALL SCREW COMPANY, LLC ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: WALTON, DENNIS FREDERICK
Publication of US20010018850A1 publication Critical patent/US20010018850A1/en
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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16CSHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/30Parts of ball or roller bearings
    • F16C33/37Loose spacing bodies
    • F16C33/3713Loose spacing bodies with other rolling elements serving as spacing bodies, e.g. the spacing bodies are in rolling contact with the load carrying rolling elements
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16HGEARING
    • F16H25/00Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20Screw mechanisms
    • F16H25/22Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members
    • F16H25/2204Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16HGEARING
    • F16H35/00Gearings or mechanisms with other special functional features
    • F16H35/10Arrangements or devices for absorbing overload or preventing damage by overload
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16HGEARING
    • F16H57/00General details of gearing
    • F16H57/04Features relating to lubrication or cooling or heating
    • F16H57/048Type of gearings to be lubricated, cooled or heated
    • F16H57/0497Screw mechanisms
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00Machine element or mechanism
    • Y10T74/18Mechanical movements
    • Y10T74/18568Reciprocating or oscillating to or from alternating rotary
    • Y10T74/18576Reciprocating or oscillating to or from alternating rotary including screw and nut
    • Y10T74/18728Backlash
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00Machine element or mechanism
    • Y10T74/18Mechanical movements
    • Y10T74/18568Reciprocating or oscillating to or from alternating rotary
    • Y10T74/18576Reciprocating or oscillating to or from alternating rotary including screw and nut
    • Y10T74/18744Lubrication
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00Machine element or mechanism
    • Y10T74/19Gearing
    • Y10T74/19642Directly cooperating gears
    • Y10T74/19698Spiral
    • Y10T74/19702Screw and nut

Definitions

  • the present invention claims the priority of United Kingdom patent application Serial No. 9930356.2 filed Dec. 22, 1999 and relates to a self-lubricating ballscrew comprising a screwshaft, a ballnut surrounding the screwshaft and provided with a re-circulating path for a plurality of balls which roll between the ballnut and the screwshaft when the ballscrew is in use, and lubrications means in contact with the helical groove of the screwshaft to provide lubrication therefor.
  • the present invention seeks to provide a remedy for one or more of these drawbacks.
  • the present invention is directed to a lubricating ballscrew as set out in the opening paragraph of the present specification, in which the self-lubricating means comprises a lubricant impregnated solid having an elongate portion which follows the path of and is received in the helical groove of the screwshaft, the cross-section of that portion being different from that of the said groove, so that the contact region between the said portion and the said groove coincides with the lines of contact between the balls and the screwshaft, and the deposit of lubricant is concentrated on those lines.
  • the said portion has a section which is at least in part polygonal, for example rectangular or square, the cross-section of the groove being a curve, for example semi-circular in shape.
  • the length of the said portion corresponds to substantially one pitch of the helical groove.
  • the lubrication means are secured to the ballnut.
  • At least a portion of the lubricating means may be received between the ballnut and the screwshaft.
  • a desired pressure of the lubricating means against the screwshaft may be obtained if the lubricating means comprise two semi-cylindrical segments, each having one end retained within the ballnut between the ballnut and the screwshaft and another end projecting outwardly from the ballnut in an axial direction along the screwshaft, the segments being urged towards one another by spring means.
  • Such lubricating means may be provided at both ends of the ballnut.
  • FIG. 1 shows a side view of the ballscrew
  • FIG. 2 shows an underneath view of a segment of the lubricating means of the ballscrew shown in FIG. 1;
  • FIG. 3 shows a portion of the screwshaft of the ballscrew shown in FIG. 1;
  • FIG. 4 shows diagrammatically a cross-sectional view of a portion of the lubricating means where it contacts a helical groove of the screwshaft of the ballscrew shown in FIG. 1;
  • FIG. 5 shows a cross-sectional view through a ball engaging a groove of the screwshaft of the ballscrew shown in FIG. 1 .
  • the ballscrew shown in FIG. 1 comprises a screwshaft 10 provided with a helical groove 12 around its outside, and a ballnut 14 surrounding the screwshaft 10 and provided with a re-circulating path 16 in its interior. Balls 18 are provided within the ballnut in the re-circulating path and in engagement with the helical groove 12 of the screwshaft.
  • Two pairs of semi-cylindrical lubricant impregnated polymer segments 20 are provided, one at each end of the ballnut 14 .
  • Each pair of segments 20 is arranged to surround the screwshaft 10 , with respective ends of each segment received within that end of the ballnut 14 between the ballnut , 4 and the screwshaft 10 .
  • the remainder of each segment of the pair 20 extends axially outwardly away from the ballnut 14 Those ends of the segments 20 which are outside of the ballnut 14 are urged towards one another by means of a circular spring 22 .
  • Each segment 20 has an interior surface as shown in FIGS. 2 and 4.
  • it has an elongate portion 24 which projects inwardly from the main body of the segment 20 , and which follows the path of a portion of the helical groove 12 and is received therein.
  • the cross-section of the portion 24 is generally polygonal, in this case substantially rectangular in shape, whereas the cross-section of the groove 12 is generally semi-circular.
  • the region of contact between a segment 20 and the groove 12 where lubricant is deposited thereon, is substantially only in the region of the contact lines 26 corresponding to the contact lines 26 between the balls 18 and the groove 12 .
  • Each segment 20 has a portion 24 which corresponds in length to half a pitch of the groove 12 , so that each pair has portions corresponding in length in total to substantially one pitch of the groove 12 .
  • the segments 20 may be made shorter in actual length and retained wholly within the ballnut 14 .
  • the circular spring 22 may be a close wound wire spring, such as is commonly used in shaft lip seals.
  • the polymer segments 20 may comprise the material sold under the trade name MICROPOLY, manufactured by Phymet Inc., of 820 pleasant Valley, P.O. Box 486, Springboro, Ohio 45066, United States of America.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transmission Devices (AREA)

Abstract

A self-lubricating ballscrew has a screwshaft and a ballnut surrounding the screwshaft and provided with a re-circulating path for a plurality of balls which roll between the ballnut and the screwshaft when the ballscrew is in use. Lubrication means are in contact with the helical groove of the screwshaft to provide lubrication therefor. The self-lubricating means comprises a lubricant impregnated solid having an elongate portion which follows the path of and is received in the helical groove of the screwshaft. The cross-section of that portion is different from that of the said groove, so that the contact region between the said portion and the said groove coincides with the lines of contact between the balls and the screwshaft. The deposit of lubricant is thereby concentrated on those lines.

Description

FIELD OF THE INVENTION
The present invention claims the priority of United Kingdom patent application Serial No. 9930356.2 filed Dec. 22, 1999 and relates to a self-lubricating ballscrew comprising a screwshaft, a ballnut surrounding the screwshaft and provided with a re-circulating path for a plurality of balls which roll between the ballnut and the screwshaft when the ballscrew is in use, and lubrications means in contact with the helical groove of the screwshaft to provide lubrication therefor.
The present invention seeks to provide a remedy for one or more of these drawbacks.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a lubricating ballscrew as set out in the opening paragraph of the present specification, in which the self-lubricating means comprises a lubricant impregnated solid having an elongate portion which follows the path of and is received in the helical groove of the screwshaft, the cross-section of that portion being different from that of the said groove, so that the contact region between the said portion and the said groove coincides with the lines of contact between the balls and the screwshaft, and the deposit of lubricant is concentrated on those lines.
Preferably, the said portion has a section which is at least in part polygonal, for example rectangular or square, the cross-section of the groove being a curve, for example semi-circular in shape.
Advantageously, to balance the lubricating effect of the lubrication means against the friction it causes, the length of the said portion corresponds to substantially one pitch of the helical groove.
Advantageously, the lubrication means are secured to the ballnut.
At least a portion of the lubricating means may be received between the ballnut and the screwshaft.
A desired pressure of the lubricating means against the screwshaft may be obtained if the lubricating means comprise two semi-cylindrical segments, each having one end retained within the ballnut between the ballnut and the screwshaft and another end projecting outwardly from the ballnut in an axial direction along the screwshaft, the segments being urged towards one another by spring means.
Such lubricating means may be provided at both ends of the ballnut.
BRIEF DESCRIPTION OF THE DRAWING
An example of a self-lubricating ballscrew made in accordance with the present invention is illustrated in the accompanying drawings, in which:
FIG. 1 shows a side view of the ballscrew;
FIG. 2 shows an underneath view of a segment of the lubricating means of the ballscrew shown in FIG. 1;
FIG. 3 shows a portion of the screwshaft of the ballscrew shown in FIG. 1;
FIG. 4 shows diagrammatically a cross-sectional view of a portion of the lubricating means where it contacts a helical groove of the screwshaft of the ballscrew shown in FIG. 1; and
FIG. 5 shows a cross-sectional view through a ball engaging a groove of the screwshaft of the ballscrew shown in FIG. 1.
DETAILED DESCRIPTION OF THE DRAWINGS
The ballscrew shown in FIG. 1 comprises a screwshaft 10 provided with a helical groove 12 around its outside, and a ballnut 14 surrounding the screwshaft 10 and provided with a re-circulating path 16 in its interior. Balls 18 are provided within the ballnut in the re-circulating path and in engagement with the helical groove 12 of the screwshaft.
Two pairs of semi-cylindrical lubricant impregnated polymer segments 20 are provided, one at each end of the ballnut 14.
Each pair of segments 20 is arranged to surround the screwshaft 10, with respective ends of each segment received within that end of the ballnut 14 between the ballnut ,4 and the screwshaft 10. The remainder of each segment of the pair 20 extends axially outwardly away from the ballnut 14 Those ends of the segments 20 which are outside of the ballnut 14 are urged towards one another by means of a circular spring 22.
Each segment 20 has an interior surface as shown in FIGS. 2 and 4. In particular, it has an elongate portion 24 which projects inwardly from the main body of the segment 20, and which follows the path of a portion of the helical groove 12 and is received therein. As is shown more clearly in FIG. 4, the cross-section of the portion 24 is generally polygonal, in this case substantially rectangular in shape, whereas the cross-section of the groove 12 is generally semi-circular. As a result, the region of contact between a segment 20 and the groove 12, where lubricant is deposited thereon, is substantially only in the region of the contact lines 26 corresponding to the contact lines 26 between the balls 18 and the groove 12.
Each segment 20 has a portion 24 which corresponds in length to half a pitch of the groove 12, so that each pair has portions corresponding in length in total to substantially one pitch of the groove 12.
Numerous variations and modifications to the illustrated construction of ballscrew may occur to the reader without taking the resulting construction outside the scope of the present invention. To give one example only, the segments 20 may be made shorter in actual length and retained wholly within the ballnut 14. The circular spring 22 may be a close wound wire spring, such as is commonly used in shaft lip seals. The polymer segments 20 may comprise the material sold under the trade name MICROPOLY, manufactured by Phymet Inc., of 820 Pleasant Valley, P.O. Box 486, Springboro, Ohio 45066, United States of America.

Claims (11)

I claim:
1. A self-lubricating ballscrew assembly comprising an axially extending screwshaft having a helical thread defining a helical groove; a ballnut surrounding the screwshaft and provided with a re-circulating path; a plurality of balls having a predetermined diameter which roll in said path between the ballnut and said groove of the screwshaft when the ballscrew is in use; said helical groove comprising in cross section an entrance throat section of greater axial width than the diameter of said balls communicating with an arcuate radially inner ball receiving section having a bottom and having an axial width, in a portion spaced radially from said bottom, substantially equal to the said diameter of said balls to form a line contact surface on each axial side of said arcuate section of said groove limiting further radially inward travel of said balls; and a self-lubricating lubrication device in contact with the helical groove of the screwshaft to provide lubrication, wherein the self-lubricating device comprises a lubricant impregnated solid having an elongate helical portion which follows the path of and is received in the said arcuate section of the helical groove of the screwshaft, the cross-section of said elongate helical portion of the said solid providing axially spaced line contact surfaces axially spaced to correspond with said diameter of said balls received within said groove, so that the said line contact portions on said elongate portion essentially coincide with the lines of contact between the balls and the groove of said screwshaft, and the deposit of lubricant is concentrated on said lines of contact.
2. A self-lubricating ballscrew according to claim 1, wherein the said elongate portion has a section which is at least in part polygonal, the cross-section of said arcuate section being a curve.
3. A self-lubricating ballscrew according to claim 2, wherein the said elongate portion has a section which is at least in part rectangular.
4. A self-lubricating ballscrew according to claim 2, wherein the said elongate portion has a section which is at least in part square.
5. A self-lubricating ballscrew, according to claim 2, wherein the cross-section of said arcuate section of said groove is substantially semi-circular in shape.
6. A self-lubricating ballscrew, according to claim 1, wherein the length of the said elongate portion corresponds to substantially one pitch of the helical groove.
7. A self-lubricating ballscrew, according to claim 1, wherein the lubrication device is secured to the ballnut.
8. A self-lubricating ballscrew, according to claim 1, wherein at least a portion of the lubricating device is received between the ballnut and the screwshaft.
9. A self-lubricating ballscrew, according to claim 1, wherein the lubricating device comprises two semi-cylindrical segments, each have one end retained within the ballnut between the ballnut and the screwshaft and another end projecting outwardly from the ballnut in an axial direction along the screwshaft, the segments being urged towards one another by spring means.
10. A self-lubricating ballscrew, according to claim 9, wherein such lubricating segments are provided at both ends of the ballnut.
11. A self-lubricating ball screw, according to claim 1, wherein said self-lubricating device is radially spaced from said screw helical thread.
US09/745,052 1999-12-22 2000-12-20 Self-lubricating ballscrew Expired - Fee Related US6601676B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9930356A GB2357562A (en) 1999-12-22 1999-12-22 Self-lubricating ballscrew
GB9930356.2 1999-12-22
GB9930356 1999-12-22

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US20010018850A1 US20010018850A1 (en) 2001-09-06
US6601676B2 true US6601676B2 (en) 2003-08-05

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Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI221512B (en) * 2002-04-15 2004-10-01 Smc Corp Ball screw mechanism
DE102007030445B4 (en) * 2006-08-25 2019-05-16 Adient Luxembourg Holding S.À R.L. Actuator of a motor vehicle seat
JP5708638B2 (en) * 2010-03-31 2015-04-30 日本精工株式会社 Method for manufacturing ball screw nut and ball screw
EP3392528B1 (en) * 2017-04-21 2020-04-08 Goodrich Actuation Systems Limited Ballscrew lubrication
KR200487409Y1 (en) * 2017-06-21 2018-10-31 하이윈 테크놀로지스 코포레이션 Ball screw with a dust-proof and self-lubricating module

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2757548A (en) * 1954-10-07 1956-08-07 Cleveland Pneumatic Tool Co Screw scraper and wiper
US5168767A (en) * 1990-06-04 1992-12-08 Nippon Thompson Co., Ltd. Compact ball screw assembly
US5906136A (en) 1993-06-21 1999-05-25 Nsk Ltd. Ball screw lubricated with oil-containing polymer
US6023991A (en) * 1993-06-21 2000-02-15 Nsk Ltd. Ball screw lubricated with oil-containing polymer
US6119813A (en) * 1997-06-10 2000-09-19 Nsk Ltd. Lubricant feeder and linear apparatus
US6216821B1 (en) * 1997-07-24 2001-04-17 Nsk Ltd. Lubricating apparatus for ball screw
US6338285B2 (en) * 1996-06-17 2002-01-15 Nsk Ltd. Feed screw device

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3367911B2 (en) * 1999-02-26 2003-01-20 Thk株式会社 Lubricating oil supply device and rolling element screw device using the same

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2757548A (en) * 1954-10-07 1956-08-07 Cleveland Pneumatic Tool Co Screw scraper and wiper
US5168767A (en) * 1990-06-04 1992-12-08 Nippon Thompson Co., Ltd. Compact ball screw assembly
US5906136A (en) 1993-06-21 1999-05-25 Nsk Ltd. Ball screw lubricated with oil-containing polymer
US6023991A (en) * 1993-06-21 2000-02-15 Nsk Ltd. Ball screw lubricated with oil-containing polymer
US6338285B2 (en) * 1996-06-17 2002-01-15 Nsk Ltd. Feed screw device
US6119813A (en) * 1997-06-10 2000-09-19 Nsk Ltd. Lubricant feeder and linear apparatus
US6216821B1 (en) * 1997-07-24 2001-04-17 Nsk Ltd. Lubricating apparatus for ball screw

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US20010018850A1 (en) 2001-09-06
GB9930356D0 (en) 2000-02-09
GB2357562A (en) 2001-06-27

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